Pacific Duckclam Shell, Raeta undulata

Pacific Duckclam Shell, Raeta undulata. Shell collected off the beach of Punta Chivato, Baja California Sur, April 2025. Size: 7.1 cm (2.8 inches) x 5.5 cm (2.2 inches) x 1.8 cm (0.8 inches).  Collection, photograph and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Pacific Duckclam Shell, Raeta undulata. Shell collected off the beach of Punta Chivato, Baja California Sur, April 2025. Size: 7.9 cm (3.1 inches) x 6.0 cm (2.4 inches) x 1.9 cm (0.7 inches). Collection, photograph and identification courtesy of Colin Campbell, DVM, Punta Chivato.

Phylogeny: The Pacific Duckclam, Raeta undulata (A.A.Gould, 1851), is a bivalve mollusk in the Anatinellidae Family of Duckclams. The Raeta Genus is one of two genera in the subfamily Kymatoxinae, and there are five species in the Raeta Genus. The Anatinellidae Family name originates from the Latin words meaning “little duck-like”, which yields the common name duckclam.

Description: Pacific Duckclam Shells are ovate to trigonal in outline and inflated in profile. The shells are thin and often translucent. The anterior is broadly rounded. The posterior is longer and more sharply rounded. A ridge often delineates the posterior end, and there is a narrow gap between valves at the posterior end. These shells are sculpted with strong commarginal undulations, which are most prominent away from the ventral margin. Very fine commarginal and radial striae are also present. Inside the shell, the resilifer (spoon-shaped process at hinge) projects ventrally. These shells are white with a thin, silky, cream colored periostracum. Pacific Duckclam Shells reach a maximum of 11.0 cm (4.7 inches) in length.

Habitat and Distribution: Pacific Duckclams are found on sand substrates in the protected waters of bays and the foreshore. They live in the intertidal zone, and to depths of 20 m (66 feet). They are a subtropical to tropical Eastern Pacific species that are found in all Mexican waters of the Pacific Ocean.

Ecology and Behavior: Pacific Duckclams are suspension feeders, which feed on plankton and suspended organic matter. They are preyed upon by shorebirds, crabs, fish, gastropods, and sea stars. Pacific Duckclams are gonochoric and reproduce sexually, through broadcast spawning. Their engagement in any type of commensal, parasitic, or symbiotic relationship has not been formally documented.

Conservation: From a conservation perspective the Pacific Duckclam has not been formally evaluated.

Synonyms: Labiosa (Raeta) gabbi, Labiosa gabbi, Lutraria gardnerae, Lutraria hasletti, Lutraria undulata, and Raeta gibbosa.